The present invention relates to a hydraulic mechanism such as a motor or a pump comprising a cylinder block that is suitable for rotating about an axis of rotation in a stationary casing and that has a plurality of cylinders in which pistons are disposed that are suitable for co-operating with a cam that is secured to or integral with the casing, the cylinders extending radially relative to the axis of rotation and being connected by cylinder ducts to communication orifices disposed in a communication face of the cylinder block that is perpendicular to the axis of rotation, the motor further comprising a distribution cover that forms a portion of the casing, and an internal fluid distributor that is non-rotary relative to said cover, the cover having feed and discharge ducts that pass through a zone corresponding to an axial projection of the cylinders and that extend between an outside face and an inside face of said cover, the internal distributor having distribution ducts that extend between a connection face that co-operates with said inside face for the purpose of selectively connecting the distribution ducts to the feed and discharge ducts, and a distribution face that is perpendicular to the axis of rotation and that is disposed against the communication face in such a manner as to cause the distribution orifices of said distribution ducts to communicate with the communication orifices while the cylinder block is rotating.
In this type of mechanism, when it is a motor, the drive outlet is formed by a member that is constrained to rotate with the cylinder block. For example, said member is constituted by a portion of the cylinder block that forms a flange that projects beyond the casing and to which an article to be driven can be fastened, or else said member can be constituted by a drive shaft that is constrained to rotate with the cylinder block. In particular, the shaft is engaged in a central bore in the cylinder block and is constrained to rotate therewith by means of fluting.
This type of motor is in very wide use for driving all types of moving member, in particular vehicle displacement members for enabling a vehicle to move.
An analogous mechanism can be used as a pump for feeding a hydraulic circuit with fluid under pressure.
Usually, such mechanisms are used on vehicles and are situated in an environment also occupied by the other parts and members of the vehicle. It is also desirable for the hydraulic connection to be easily accessible, which is why the feed and discharge ducts have their outlets situated in the outside face of the distribution cover.
An object of the present invention is to improve the known state of the art for a hydraulic mechanism of the above-mentioned type, by increasing its compactness.
This object is achieved by means of the fact that, in a zone defined radially outwards by end-wall portions of the cylinders, a transverse face of the cylinder block is provided with an axial setback in which at least a portion of the distributor is disposed, in which portion the distribution face is situated, the communication face being provided in a plane surface of said setback.
The overall axial size of the hydraulic mechanism is reduced by a length corresponding to the depth of the axial setback, advantageous use being made of said setback for receiving a portion of the distributor. This configuration in no way hinders access to the hydraulic connection of the feed and discharge ducts, because said ducts remain situated in the outside face of the distribution cover. It should also be noted that the weight of the mechanism is reduced in proportions corresponding to the weight of material removed from the setback. It should also be noted that the improvement procured by the invention is entirely compatible with the use of a conventional distributor, as explained below, and with, as a drive outlet member of the motor, a shaft engaged in the central bore of the cylinder block, regardless of whether or not said shaft is a through shaft.
Advantageously, the setback extends to a radial plane situated between two transverse planes defined by the envelope of at least some of the pistons. In which case, it is advantageous, at least for the cylinders in which said at least some of the pistons slide, for the cylinder ducts to have duct segments that are offset towards that side of the cylinder block that is opposite from the setback relative to the axes along which the pistons slide.
These configurations make it possible to give the axial setback a depth that is relatively large, thereby improving the compactness of the mechanism.
Advantageously, on its inside face, the distribution cover has an extension that penetrates into the setback.
Thus, a portion of the distribution cover that is necessary for it to co-operate properly with the internal distributor can also be received in the setback, thereby further increasing the compactness of the mechanism.
Advantageously, the extension of the distribution cover and the setback have facing cylindrical faces, between which a rotary bearing is provided.
The rotary bearing can, in particular, comprise a journal bearing or a needle roller bearing. It makes it possible to improve the rigidity of the cylinder block by supporting said cylinder block in the setback, in such a manner as to avoid any tendency, in operation, for the cylinder block to tilt or to deform towards the setback.